OPR-J311-KR-19Chandeleur IslandsChandeleur Islands, LouisianaDavid Evans and AssociatesH13267824 NM East of Brenton IslandsLouisianaUnited States400002019Jonathan L. Dasler, PE, PLS, CHNavigable Area2019-06-192019-10-132020-01-16Multibeam Echo SounderMultibeam Echo Sounder Backscatter &Side Scan SonarmetersUTCAtlantic Hydrographic BranchAny revisions to the Descriptive Report (DR) applied during office processing are shown in red italic text. The DR is maintained as a field unit product, therefore all information and recommendations within this report are considered preliminary unless otherwise noted. The final disposition of survey data is represented in the NOAA nautical chart products. All pertinent records for this survey are archived at the National Centers for Environmental Information (NCEI) and can be retrieved via https://www.ncei.noaa.gov/. Products created during office processing were generated in NAD83 UTM 16N, MLLW. All references to other horizontal or vertical datums in this report are applicable to the processed hydrographic data provided by the field unit.ContractorDavid Evans and Associates, Inc. (DEA) conducted a hydrographic survey of the assigned area in the Chandeleur Islands. Survey H13267 was conducted in accordance with the May 21, 2019 Statement of Work and Hydrographic Survey Project Instructions June 19, 2019. The Hydrographic Survey Project Instructions reference the National Ocean Service (NOS) Hydrographic Surveys Specifications and Deliverables Manual (HSSD) (March 2019) as the technical requirements for this project.29.573217805688.859209111129.294532588.509096Survey Limits were surveyed in accordance with the requirements in the Project Instructions and the HSSD.OPR-J311-KR-19 Assigned Survey Areasfile:///Q:/Survey/H13267_J311_KR_19/AHB_H13267/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/OPR-J311-KR-19_Assigned_Survey_Areas.PNGThe project’s survey purpose for all surveys, which was defined in the Project Instructions, is “The Chandeleur Islands is an active oil and gas exploration area, as well as a popular fishing grounds and includes the Breton National Wildlife Refuge.*1 The Chandeleur Islands were also severely impacted by recent hurricanes like Dennis and Katrina, which resulted in major erosion of the islands. Erosion, sea level rise, and sediment influx from the Mississippi River have endangered the future of these islands.*2 This area also supports a wide variety of vessel traffic and commercial and sport fishing traffic near the Mississippi Entrance Channel and includes a major portion of the safety fairway. Due to the high traffic, this project has been planned as one of a multi-year approach to update charts in this area. Before this project, this area was last surveyed by the Office of Coast Survey in 1922 and 1940. This survey will allow vessel traffic safe passage to offshore Gulf of Mexico. The purpose of this project is to provide contemporary surveys to update National Ocean Service (NOS) nautical charting products, this project will address numerous approximately charted hazards, reducing the risk to navigation. Survey data from this project is intended to supersede all prior survey data in the common area.” *1 Breton National Wildlife Refuge. Wikipedia. Retrieved 27 February 2019 *2 Moore, Laura J.; Patch, Kiki; List, Jeffery H.; Williams, S. Jeffress (2014). “The potential for sea-level-rise-induced barrier island loss: Insights from the Chandeleur Islands, Louisiana, USA”. Marine Geology. 355: 244-259. doi:10.1016/j.margeo.2014.05.022. ISSN 0025-3227The entire survey is adequate to supersede previous data.All waters in survey area Complete Coverage Option B (Refer to HSSD Section 5.2.2.3)Multibeam echosounder (MBES) data with time series backscatter was collected concurrently with side scan sonar (SSS) data to obtain complete coverage in all waters in the survey area. This coverage type follows Option B of the Complete Coverage requirement specified in Section 5.2.2 of the 2019 HSSD. Surveyed contacts and features were developed at complete coverage resolution as required by the coverage classification. Complete coverage multibeam was also obtained within the search radii for all feature disapprovals. Survey coverage was obtained within the survey area depicted in the Project Reference File (PRF) OPR-J311-KR-19_PRF_FINAL.000. Figure 2 depicts the survey outline that was obtained for H13267. In some cases, holidays present in the side scan sonar mosaic were filled with complete coverage multibeam data rather than with side scan sonar data. This includes filling holidays under and around platforms as well as holidays in open, unobstructed water. This practice was approved by the Operations Branch Project Manager on December 4, 2019. Email correspondence related to this approval is included in Separate II. While performing quality control checks of the H13267 side scan data, it was noted that SSS contact positions had an across track offset when compared to the adjacent pass that increased with longer cable lengths in deeper water. Analysis lead to the conclusion there was a slight drift to port that was exaggerated with longer layback values in deep water. The analysis concluded that this could result in SSS coverage gaps in deep water when adjacent swaths passed starboard to starboard that would not be evident in the coverage mosaic due to an across track position error of the towfish due to drift. To conservatively address potential side scan coverage gaps, a decision was made to run multibeam data down split lines when adjacent side scan lines had overlap with starboard to starboard channels in deep water. This effectively covered any potential side scan coverage gaps not apparent in coverage plots that resulted from unaccounted for port drift in the side scan position. An example of the resulting multibeam coverage is shown in Figure 3. H13267 Survey Outlinefile:///Q:/Survey/H13267_J311_KR_19/AHB_H13267/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13267_Survey_Coverage.pngExample of MBES coverage from additional linesfile:///Q:/Survey/H13267_J311_KR_19/AHB_H13267/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/MBES_Additional_Splits.pngS/V Blake091.400001114.75053.360091.400001114.75053.3604.42500067.762019-10-132019-10-142019-10-152019-10-162019-11-172019-11-182019-11-202019-11-212019-11-222019-11-232019-12-152020-01-142020-01-152020-01-16The OPR-J311-KR-19 Data Acquisition and Processing Report (DAPR), submitted previously with survey H13260, details equipment and vessel information as well as data acquisition and processing procedures. There were no vessel or equipment configurations used during data acquisition that deviated from those described in the DAPR.S/V Blake824.5S/V Blakefile:///Q:/Survey/H13267_J311_KR_19/AHB_H13267/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/OPR-J311-KR-19_Blake.pngTeledyne RESONSeaBat 7101MBESEdgeTech4200SSSApplanixPOS MV 320 v5Positioning and Attitude SystemAML OceanographicMVP30-350Sound Speed SystemAML OceanographicMicro SV-XchangeSound Speed SystemAML OceanographicBaseX2Sound Speed SystemSea-Bird ScientificSBE 19Sound Speed SystemTrimbleSPS851Positioning SystemTrimbleRTXPositioning SystemMultibeam crosslines were run across the entire survey area to provide a varied spatial and temporal distribution for analysis of internal consistency within the survey data. Crossline analysis was performed using the CARIS Hydrographic Information Processing System (HIPS) Quality Control (QC) Report tool, which compares crossline data to a gridded surface and reports results by beam number. Crosslines were compared to a 2-meter CUBE surface encompassing mainscheme, fill, and investigation data for the entire survey area. The QC Report tabular output and plots are included in Separate II Crossline Comparison. DEA performed an additional crossline analysis using the NOAA Pydro Compare Grids tool to analyze the differences between gridded mainscheme depths and gridded crossline depths. Input grids were 2-meter resolution CUBE surfaces of mainscheme and crossline depths. Results from the crossline to mainscheme difference analysis are depicted in Figure 5, units are represented in meters. H13267 Crossline Differencefile:///Q:/Survey/H13267_J311_KR_19/AHB_H13267/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13267_2m_MBES_MLLW_XL-H13267_2m_MBES_MLLW_MS_depth_delta.pngERS via VDATUM0.050.168S/V Blake1.01.00.5Additional discussion of these parameters is included in the DAPR. During surface finalization in HIPS, the "Greater of the two values" option was selected, where the calculated uncertainty from Total Propagated Uncertainty (TPU) is compared to the standard deviation of the soundings influencing the node, and where the greater value is assigned as the final uncertainty of the node. The uncertainty of the finalized surfaces increased for nodes, where the standard deviation of the node was greater than the TPU. To determine if the surface grid nodes met IHO Order 1 specification, a ratio of the final node uncertainty to the allowable uncertainty at that depth was determined. As a percentage, this value represents the amount of error budget utilized by the total vertical uncertainty (TVU) at each node. Values greater than 100% indicate nodes exceeding the allowable IHO uncertainty. The resulting calculated TVU values of all nodes in the submitted finalized surfaces are shown in Figures 6 and 7.Node TVU statistics - 2m finalizedfile:///Q:/Survey/H13267_J311_KR_19/AHB_H13267/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13267_2m_MBES_MLLW_Final.QAv5.tvu_qc.pngNode TVU statistics - 4m finalizedfile:///Q:/Survey/H13267_J311_KR_19/AHB_H13267/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13267_4m_MBES_MLLW_Final.QAv5.tvu_qc.pngSurvey H13267 junctions with current survey H13266. Prior surveys H12736, H12739, H12740, H13135, and H13136 were specified as junctions in the Project Instructions for survey H13267. Figure 8 depicts H13267 and the junctioning surveys. Survey junctions with registry number H13267file:///Q:/Survey/H13267_J311_KR_19/AHB_H13267/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13267_Junctions_graphic.pngH13266400002019David Evans & Associates, Inc.NThe mean difference between H13267 and H13266 survey depths is 1 centimeter (H13267 deeper than H13266), shown in Figure 9. Distribution summary plot of survey H13267 2-meter vs H12366 2-meterfile:///Q:/Survey/H13267_J311_KR_19/AHB_H13267/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13267_2m_MBES_MLLW-H13266_MB_2m_MLLW_depth_delta.pngH12736400002015Oceans Surveys, Inc.WThe mean difference between H13267 and H12736 survey depths is 56 centimeters (H13267 deeper than H12736), shown in Figure 10. Major differences are representative of surveys impacted by subsidence over a four year period and the use of varying tidal application methods.The descriptive report for this survey reported occasional tide offsets between adjacent survey lines of 20 centimeters that were likely caused by environmental factors such as wind setup on local water levels. Survey H13267 was tide corrected using discrete zoning from National Water Level Observation Network (NWLON) station Pilots Stations East, SW Pass, LA (876-0922), which is approximately 50 nautical miles southwest of the project area.Distribution summary plot of survey H13267 2-meter vs H12736 4-meterfile:///Q:/Survey/H13267_J311_KR_19/AHB_H13267/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13267_2m_MBES_MLLW-H12736_MB_4m_MLLW_combined_depth_delta.pngH12739400002015David Evans & Associates, Inc.SThe mean difference between H13267 and H12739 survey depths is 44 centimeters (H13267 deeper than H12739), shown in Figure 11. Major differences are representative of surveys impacted by subsidence over a four year period and the use of varying tidal application methods. Prior survey H12739 was tidally corrected using Pilot Station East, SW Pass (876-0922), while current survey H13267 was corrected using ERS methods with a VDatum derived separation model.Distribution summary plot of survey H13267 2-meter vs H12739 8-meterfile:///Q:/Survey/H13267_J311_KR_19/AHB_H13267/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13267_2m_MBES_MLLW-H12739_MB_8m_MLLW_combined_depth_delta.pngH12740400002015David Evans & Associates, Inc.SThe mean difference between H13267 and H12740 survey depths is 42 centimeters (H13267 deeper than H12739), shown in Figure 12. Major differences are representative of surveys impacted by subsidence over a four year period and the use of varying tidal application methods. Prior survey H12740 was tidally corrected using Pilot Station East, SW Pass (876-0922), while current survey H13267 was corrected using ERS methods with a VDatum derived separation model.Distribution summary plot of survey H13267 2-meter vs H12740 4-meterfile:///Q:/Survey/H13267_J311_KR_19/AHB_H13267/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13267_2m_MBES_MLLW-H12740_MB_4m_MLLW_1of1_depth_delta.pngH13135400002018LeidosWThe mean difference between H13267 and H13135 survey depths is 35 centimeters (H13267 deeper than H13135), shown in Figure 13. Major differences are representative of surveys impacted by subsidence over a one year period and the use of varying tidal application methods. According to the Descriptive Report for the prior survey, H13135 used ERS with Poor Mans VDATUM for Vertical Control methods where survey H13267 used ERS methods relying on the published VDATUM model for the area. Using prior data available on the National Centers for Environmental Information (NCEI) website, the separation model used for survey H13135 was recreated and compared to the separation model used for survey H13267. The prior model was reconstructed by computing a difference surface between the combined MLLW and ellipsoid bathymetry grids available for survey H13135. The hydrographer found up to a 19-centimeter difference between the two models at the survey junction.Distribution summary plot of survey H13267 2-meter vs H13135 2-meterfile:///Q:/Survey/H13267_J311_KR_19/AHB_H13267/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13267_2m_MBES_MLLW-H13135_MB_2m_MLLW_Combined_depth_delta.pngH13136400002018LeidosWThe mean difference between H13267 and H13136 survey depths is 45 centimeters (H13267 deeper than H13136), shown in Figure 14. Major differences are representative of surveys impacted by subsidence over a one year period and the use of varying tidal application methods. According to the Descriptive Report for the prior survey, H13136 used ERS with Poor Mans VDATUM for Vertical Control methods where survey H13267 used ERS methods relying on the published VDATUM model for the area. Using prior data available on the National Centers for Environmental Information (NCEI) website, the separation model used for survey H13136 was recreated and compared to the separation model used for survey H13267. The prior model was reconstructed by computing a difference surface between the combined MLLW and ellipsoid bathymetry grids available for survey H13136. The hydrographer found a 20-centimeter difference between the two models at the survey junction.Distribution summary plot of survey H13267 2-meter vs H13136 2-meterfile:///Q:/Survey/H13267_J311_KR_19/AHB_H13267/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13267_2m_MBES_MLLW-H13136_MB_2m_MLLW_Final_Depth_depth_delta.pngQuality control is discussed in detail in Section B of the DAPR. Results from weekly position checks and weekly multibeam bar checks are included in Separate I Acquisition and Processing Logs of this report. Sound speed checks can be found in Separate II Sound Speed Data Summary of this report. Multibeam data were reviewed at multiple levels of data processing including: CARIS HIPS conversion, subset editing, and analysis of anomalies revealed in CUBE surfaces.None ExistThere were no conditions or deficiencies that affected equipment operational effectiveness.None ExistThere were no other factors that affected corrections to soundings.Approximately 20 minute intervals An AML Oceanographic Moving Vessel Profiler (MVP) was the primary instrument used to acquire sound speed readings during multibeam operations. Additional discussion of sound speed methods can be found in the DAPR. For H13267 survey operations, casts were distributed both temporally and spatially based on observed changes in sound speed profiles. Sound speed readings were applied in CARIS using the nearest in distance within a one-hour interval. All sound speed measurements were made within 500 meters of the survey limits. Survey speeds were maintained to meet or exceed along-track sounding density requirements and side scan sonar ensonification requirements. Multibeam data and side scan mosaics were thoroughly reviewed for holidays and areas of poor-quality coverage due to biomass, vessel wakes, or other factors. Side scan sonar contacts were developed with multibeam sonar to obtain a least depth of the contact using Complete Coverage requirements. Complete coverage multibeam was acquired inside the disproval radii for assigned charted features and over all new features. Additional discussion of coverage methods can be found in the DAPR.DensityThe sounding density requirement of 95% of all nodes, populated with at least five soundings per node, was verified by analyzing the density layer of each finalized surface. Individual surface results are stated in Figures 15 and 16.Node density statistics - 2m finalizedfile:///Q:/Survey/H13267_J311_KR_19/AHB_H13267/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13267_2m_MBES_MLLW_Final.QAv5.density.pngNode density statistics - 4m finalizedfile:///Q:/Survey/H13267_J311_KR_19/AHB_H13267/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/H13267_4m_MBES_MLLW_Final.QAv5.density.pngData reduction procedures for survey H13267 are detailed in the DAPR. Summary multibeam and side scan sonar processing logs are included in Separate I of this report.All sounding systems were calibrated as detailed in the DAPR.Multibeam backscatter was logged in Hypack 7k format and included with the H13267 digital deliverables. Data were processed periodically in CARIS HIPS to evaluate backscatter quality, but the processed data is not included with the deliverables. For data management purposes, the names of multibeam crosslines have been appended with the suffix XL. This change was made to HIPS files only. The original file names of raw data files (Hypack HSX and 7k) have been retained.CARISHIPS/SIPS10.4.5Chesapeake Technology, Inc.SonarWiz7.04.01NOAA Profile Version 5.7A detailed listing of all data processing software is included in the OPR-J311-KR-19 DAPR.H13267_MB_2m_MLLWCARIS Raster Surface (CUBE)224.14663.838NOAA_2mComplete MBESH13267_MB_2m_MLLW_FinalCARIS Raster Surface (CUBE)224.14640.000NOAA_2mFinalized Complete MBESH13267_MB_4m_MLLWCARIS Raster Surface (CUBE)424.13563.541NOAA_4mComplete MBESH13267_MB_4m_MLLW_FinalCARIS Raster Surface (CUBE)436.00063.541NOAA_4mFinalized Complete MBESH13267_SSSAB_1m_600kHz_1of1SSS Mosaic10.0000.000N/A100% SSSBathymetric grids were created relative to Mean Lower Low Water (MLLW) in CUBE format using Complete Coverage resolution requirements as specified in the HSSD. Designated Soundings A total of three soundings in H13267 were designated in bathymetric data to facilitate feature management for inclusion in the H13267 Final Feature File (FFF). No soundings were designated to override the gridded surface model.CARIS HDCS Navigation Sources On January 15, 2020 (DN015), a review of the initial SBET export_Mission_1_DN015_BL.out using POSPac Automated QC Tool indicated various systematic vertical inconsistencies due to unexplained short term Dead Reckoning modes and GNSS Satellite dropouts of the POS MV system. This resulted in poor vertical solutions of the data, identifiable in the “GPSheight” records within CARIS. Errors were observed on the order of 10 to 30 centimeters. These inconsistencies were not observable in real-time monitoring. Data were inspected in both the NOAA Pydro AutoQC tool and in CARIS subset editor. To correct these inconsistencies, where prudent to correct for the errant vertical solutions, the SBET was interpolated using NOAA Pydro AutoQC and re-applied to DN015 along with an updated RMS file. Upon application, close inspection in subset editor verified improved vertical alignment with crosslines and other overlapping data. The interpolated portions of the SBET impact the following eight lines: 2020BL0150144 2020BL0150303 2020BL0150428 2020BL0150554 2020BL0150613 2020BL0150806 2020BL0151035 2020BL0151214_XL See Figure 17 for details of interpolation durations and Figure 18 for details of the interpolated SBET. Lines with interpolated SBET, and details of segment count and durationfile:///Q:/Survey/H13267_J311_KR_19/AHB_H13267/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/Interpolated_Segment_Duration.pngPortions of SBET interpolated. Note vertical jumps on top graphs, and resultant interpolation on bottom graphfile:///Q:/Survey/H13267_J311_KR_19/AHB_H13267/01_SAR/Reports/Survey/Descriptive_Report/Report/SupportFiles/SBET_Interpolation.pngA summary of the horizontal and vertical control for survey H13267 follows.Mean Lower Low WaterERS via VDATUMOPR-J311-KR-19_VDatum2_xyNAD83-MLLW_geoid12b.csarThe separation model listed in Table 13 was provided with the Project Instructions and used for sounding correction within the assigned survey area. Realtime navigation for all MBES survey lines were overwritten with post-processed navigation solutions in SBET format. Post-processed solutions were generated using Applanix POSPac MMS using the Trimble CenterPoint RTX option which relies on precise satellite orbit and timing information to create centimeter level positioning and elevation without the use of traditional local base stations. Information on survey control is detailed in the DAPR.North American Datum 1983Projected UTM 16English Turn, LA (293 kHz)Real-time positioning for side scan sonar operations was provided by differential GPS using corrections received from the US Coast Guard National Differential GPS (NDGPS) coverage network from differential beacons at English Turn, LA (293 kHz). The Federal Aviation Administration Wide Area Augmentation System (FAA WAAS) was enabled to be active if the English Turn station experienced periods of down time. The chart comparison was performed by comparing H13267 survey depths to a digital surface generated from electronic navigational charts (ENCs) covering the survey area. A 50-meter product surface was generated from a triangular irregular network (TIN) created from the ENC’s soundings, depth contours, and depth features. The 50-meter HIPS product surface of the entire survey area was generated from the 2-meter CUBE surface. The chart comparison was conducted by creating and reviewing a difference surface using the ENC surface and survey surface as inputs. The chart comparison also included a review of all assigned charted features within the survey area. The results of the comparison are detailed below. The relevant charts used during the comparison were reviewed to check that all US Coast Guard (USCG) Local Notice to Mariners (LNMs) issued during survey acquisition, and impacting the survey area, were applied and addressed by this survey. A charted fish haven (authorized min 14 fms) was located within the survey area. A submerged decommissioned platform was found within the charted obstruction area. The least depth of this feature is less than the authorized minimum depth of the fish haven. As such, a new obstruction was generated for this feature and included in the FFF. The feature’s least depth is deeper than 66 feet, therefore a danger to navigation was not issued. This fish haven is part of the Mississippi Department of Marine Resources’ (MDMR) Rigs to Reefs Program and has been designated as MP 138.US3GC04M250000632019-08-012019-11-19US4LA33M80000362019-08-012019-12-04US4LA34M80000362019-08-012019-11-13 No Dangers to Navigation (DtoNs) were submitted for this survey. This survey contains three assigned charted wrecks labeled Position Approximate (PA) in the southern extents of H13267. All three features are assigned as charted wreck (PA) with depth unknown. These were disproved inside an assigned disproval radius with 100% MBES coverage. The charted wrecks have been included in the FFF with a description of ‘Delete’. All uncharted features are portrayed in the FFF as surveyed and attributed with the description of ‘New’.No channels exist within the survey extents. There are no precautionary areas, safety fairways, traffic separation schemes, or pilot boarding areas within the survey limits. Uncharted lights and sound signals were present on all three platforms observed in the survey area. According to the Light List, the USCG does not generally include private aids located on offshore structures in the document.No Maritime Boundary Points were assigned for this survey.Five bottom samples were acquired on December 15, 2019 (DN349). The bottom sampling plan followed suggested sample locations included in the Project Reference File (PRF) provided. Minor adjustments were made to the recommended sampling locations in order to sample the varying bottom types observed in the side scan data. This modification was approved by the Contracting Officer’s Representative (COR). Correspondence is included in Appendix II Supplemental Survey Records & Correspondence of this report.No overhead features exist for this survey.There are 17 assigned submerged pipelines in the survey extents for H13267. These features were carefully reviewed for any portion of pipeline that was exposed or posed a risk to navigation. These pipelines are included in the FFF with a description of 'Retain' due to the inability of the field unit to determine if pipelines are buried. A pipeline report included in Appendix II, was submitted to the BSEE on February 11, 2020, reporting sections of exposed or unburied pipeline visible in the MBES and SSS data. The report indicates the positions of the start and end points of sections of what appear to be exposed pipelines based on interpretation of multibeam data. Due to the inability to accurately depict the location and orientation of all exposed pipelines with a single line segment, these features have been included in the FFF with a description of 'New', should further action be required after survey submittal. It is not the hydrographer’s intention that these pipeline features be used as source information for charting without further validation of origin. There are seven assigned platforms and one assigned wellhead charted within the survey extents of H13267. The northernmost production platform charted in the survey area was not observed visually. The platform was disproved in an assigned disproval radius with 100% MBES coverage. The platform is included in the FFF with a description of ‘Delete’. They hydrographer recommends removing this platform from the charts. The production platform in the northeastern extents of the survey area was disproved visually and in an assigned disproval radius with 100% MBES coverage. The platform is included in the FFF with a description of 'Delete'. The hydrographer recommends removing this platform from the charts. The ARENA-OFFSHORE-116-1 production platform charted in the western extents of the survey area was positioned with MBES approximately 17 meters off station. The platform is included in the FFF with a description of 'New'. The hydrographer recommends updating the platform to the surveyed position. The CH-MP-120-1-CE production platform charted in the western extents of the survey area was positioned with MBES approximately 25 meters off station. The platform is included in the FFF with a description of 'New'. The hydrographer recommends updating the platform to the surveyed position. The production platform charted in the western extents of the survey area was positioned with MBES approximately 39 meters off station. The platform is included in the FFF with a description of 'New'. The hydrographer recommends updating the platform to the surveyed position. The VPI-MP-125-3 production platform charted in the southwest extent of the survey area was disproved in an assigned disproval radius with 100% MBES coverage. The platform is included in the FFF with a description of 'Delete'. The hydrographer recommends removing this platform from the charts. The VPI-MP-124-2 production platform charted in the southwest extent of the survey area was disproved in an assigned disproval radius with 100% MBES coverage. The platform is included in the FFF with a description of 'Delete'. The hydrographer recommends removing this platform from the charts. The wellhead, Well (cov 14 fms), charted in the southern extent of the survey area was not observed inside an assigned disproval radius with 100% MBES coverage. The wellhead has been included in the FFF with a description of 'Delete'.No ferry routes or terminals exist for this survey.No abnormal seafloor and/or environmental conditions exist for this survey.No present or planned construction or dredging exist within the survey limits.No new surveys or further investigations are recommended for this area.No new insets are recommended for this area.As Chief of Party, field operations for this hydrographic survey were conducted under my direct supervision, with frequent personal checks of progress and adequacy. I have reviewed the attached survey data and reports.All field sheets, this Descriptive Report, and all accompanying records and data are approved. All records are forwarded for final review and processing to the Processing Branch.The survey data meets or exceeds requirements as set forth in the NOS Hydrographic Surveys and Specifications Deliverables, Field Procedures Manual, Letter Instructions, and all HSD Technical Directives. These data are adequate to supersede charted data in their common areas. This survey is complete and no additional work is required.Jonathan L. Dasler, PE, PLS, CHNSPS/THSOA Certified Hydrographer, Chief of Party2020-03-20Jason Creech, CHNSPS/THSOA Certified Hydrographer, Charting Manager / Project Manager2020-03-20Callan McGriff, EITIHO Cat-A Hydrographer, Lead Hydrographer2020-03-20Steven LoyIHO Cat-A Hydrographer, Lead Hydrographer2020-03-20Data Acquisition and Processing Report2020-02-07